This could be user error or lack of knowledge on my part, but I've been in the process of renaming all of the PCs at the company I work for. They started out small with no naming scheme is place but since we're growing I figured now's the time. Anyway, when creating unattended clients I have been using %ComputerName%--%UserName%. Before renaming the PCs I might have a name such as Dell_Desktop--John. However, after PCs reboot after the renaming process I'm ending up with something more like NEWPCNM--NEWPCNM$

Hope my explanation makes sense.